/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package io.druid.sql.calcite.expression;

import io.druid.sql.calcite.planner.PlannerContext;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.sql.SqlFunction;

import java.util.List;

public interface SqlExtractionOperator
{
  /**
   * Returns the SQL operator corresponding to this aggregation function. Should be a singleton.
   *
   * @return operator
   */
  SqlFunction calciteFunction();

  /**
   * Returns the Druid {@link RowExtraction} corresponding to a SQL {@code RexNode}.
   *
   * @param plannerContext SQL planner context
   * @param rowOrder       order of fields in the Druid rows to be extracted from
   * @param expression     expression meant to be applied on top of the table
   *
   * @return (columnName, extractionFn) or null
   *
   * @see Expressions#toRowExtraction(PlannerContext, List, RexNode)
   */
  RowExtraction convert(
      PlannerContext plannerContext,
      List<String> rowOrder,
      RexNode expression
  );
}
